Brake Drum Paint Burnt Off (On one drum only)

[earlymopar]

I was adjusting my tailpipe position and noticed some of the passenger side rear brake drum black paint was missing (all along the edge on the open side of the drum). I couldn't tell if I was seeing the red oxide primer or rust but I could also see black dust on the wheel that was not brake shoe dust. I should mention that the rear end (from U joints to 3rd member to brake drums) is all new or rebuilt and has about 50 miles on it. In that drive there was never the sound of scraping, dragging, etc. The only thing I did other than regular driving was one attempt at bedding the brakes in on a long steep hill on a country road.

After seeing the paint problem, I removed the wheel/tire and saw no signs of heat, especially on the wheel or the mounting surface of the drum. The drum came right off so was not adjusted too tight. After looking over the drum, the paint has definitely burnt off as thought. Looking over the shoes, backing plates, drum internal surfaces and all internal hardware, there are no signs of wear that would indicate a high spot or single point of contact. Later I found one surface that showed an indication of being hot and that was on the diamond shaped retainer on the upper post (the upper-most gold piece in my pictures of the internal parts). That part has surface bubbles in the plating which I know were not there when I assembled everything. I should also mention that this burnt paint / heat issue only shows on the passenger side rear. The driver's side is OK (and both drums, etc. have the same paints applied).

I'd be interested in your comments. I should mention that I'm not online often but will watch for notices.

Thanks much.

 

[dano]

Was there a cure procedure on the paint you used? I know with the highs temp stuff I've used it needs a few lower temperature bakes to cure and reach max strength. So if you did a bed in, you might have burned it off.

 

[earlymopar]

There was a cure process and it was followed for both the primer and top coats used on both drums. I also believe that the heat from bedding in heated up the drum and burnt off the paint. One additional "finding" was that my new emergency brake cable requires (2) snap rings to keep it in place on the frame mounted bracket. I didn't notice that at the time I was assembling everything and only added one. That meant that the cable was not pulling on the shoe on that side.